Method of hardening and toughening broken-mineral aggregates consisting of trap rock, limestones, sandstones, and types of shale rocks



Patented Oct. 18, 1927.

UNITED STATES 1,645,891 PATENT OFFICE.

1 JOSEPH HAY AMIES, OF PHILADELPHIA, PENNSYLVANIA.

METHOD OF HARDENING AND TOUGHENING BROKEN-MINERAL AGGREGATES CON-SISTING OF TRAP ROCK, LIMESTONES, SANDSTONES, AND TYPES OF SHALE ROCKS.I

No Drawln g.

One of the objects of this improvement. is to increase the hardness andtoughness of broken granite, limestone, sandstone, and types of shalerocks. Broken stones'now ad- 5 mitted to be used for bituminous andalkaline concrete manufacture, must provide, ten centigrades ofco-efiiciency. Otherwise, they would not be accepted by the engineersand bureaus of highways. The hardest and toughest mineral known is thediamond. This is stated as one hundred. Broken stone must provide atoughness and hardness, equal to one-tenth of this standard, in order tobe acceptable for concrete making. This degree of hardness and toughnessis termed, tencentigrades of coefliciency. This is equal to the hardnessand toughness of the set of cement binders. It is called theco-efficiency of the broken stones, that is, the broken stones areco-equal in toughness and hardness with" the binder, itself. Theimportance of this exacti'on lies in the fact that if either the brokenstones or the binder should be too weak to stand the exactions oftrafiic, poor concrete would result:

Another important object of this improvement is to securegreatlyfieduced cost in making concretes.

My process is as follows To each five hundred pounds, I may say, ofbroken stones placed in an agitator or mixer. I may add about ten poundsof finely granulated quick lime, whilst the same has just begun toslake. This batch quantity of broken stones, in about thirty seconds.after being placed in the said agitator, may be dumped into a shelteredbin or shed. Curing will proceed after the treated broken stones havebeen stored up. They may however, be immediately employed. Care shouldbe taken to have the broken stones clean,

' that is, free from soil, or stone dust, be-

cause these will consume the causticity of 15 the slaking lime needed inthe process. If

the stones are unclean not only will the action of the lime be weakenedbut the. already slaking lime will not secure a close touch with thebroken stone aggregates.

0 It will be seen that great expense in making concretes will be savedby the above process, because broken granite that is naturally hardenough to serve in the manu facture of concretes is very confined. At

36 least seven-tenths of the territories of the mal voids of the stoneaggregates appeared Application filed August 12, 1926. Serial No.128,906.

United States, must, for reasons, be deprived of standard brokenaggregates. They are, for the same reasons, prohibited on the ac countof costs, in said territories. This ty e of broken granite aggregates,that attain thedemanded co-efliciency, naturally, costs at the quarriesor ledges, where broken, from three to six times more than broken softlimestones, and sandstones and shale rocks. In addition to this, owingto the distance of-haulage and freightage, the final costs of brokentrap rock granite, would give an extended expense in manufacturingconcretes, many times greater than if'the above referred to brokenlimestones and other lighter and weaker broken stones could be used. Notonly this, but broken trap rock granite weighs from one hundred to onehundred and twenty five pounds to. the cubic foot, when clean, that is.free of stone dust and soil. Whilst, the lighter broken stone, referredto, weigh no more, on an average, than forty-five to seventyvfive poundsto the cubic foot. Therefore, a ton of the lighter stone would make avery much larger bulk than would the heavier trap rock brokenaggregates, per ton. But broken stones are not sold by bulk, but byweight. The heavier stone concretes would give only a spread of four tofive square yards per ton, Whilst, the lighter broken stones would givea spread .of from seven to ten, and even, sometimes, twelve square yardsto the ton. On account of the weakness of the lighter broken stonesreferred to, they are not employed, at all, in concrete making.Therefore, important industries are prevented,

provided the said lighter and weaker broken stones could be brought upto the standard of co-efliciency, as they can be, by the herein definedprocess.

To ascertain to what extent this process would induce the said increasein hardness and toughness, standard tests were made. No increase inweight was found, yet, when the broken aggregates were sawed through andopened and subjected to magnification, it was found that no inherentmoisture seemed to be present therein. The infinitesito be filled with abluish colored substance. The aggregates that had not been subjected tothe action of the slaking lime, presented readily discernable inherentmoisture in the said voids. Moreover, where water in the said voids wasabsent or partly absent, air was present, because voids are notpermitted to be unfilled, or partly unfilled, by nature. This fact,accounts for the disintegration of rock when subjected to alternates ofair and water, and changes of temperatures. What the reaction of theslaking lime upon the inherent moisture, within the broken stones mightbe has not been learned. A continuation of tests showed a considerableincrease in the toughness and hardness of the broken granite, andlimestone and sandstone and shale rocks. These were sufiicient to raisemany of them to the standard of coetficiency. I

Even mortar made with sand and gravel and pebbles and cobbles, willbecome, as to the aggregates themselves, much harder and tougher, intime b being mixed with slaking lime. Former y it was the custom to mixthese materials with slaking lime not because there was any supposedobject in using slaking lime, but because calcium hydroxide-had notbecome commercial. It was not thought that the aggregates themselvesbecame harder and tougher, but only the binder. itself became harder andtougher.

But, it should be observed, that it is the larger and coarser aggregatesthat protect the binders ,when associated with finer particles and thiisactually take the support of the composition when subjected to heavyweight and considerable attrition. This is shown always when mortarcomposed of lime and Portland cement binders and fine substances such assand and stone dust,'readily and quickly abraise and break up; i

It has been observed that the a gregates themselves became harder andtoug er when mortars were made with slaking lime instead of being madewith calcium hydroxide. In the latter case little increase in hardnessand toughness occurs. It takes a long time to effect this chemicalreaction in the case of mortars, even where coarser aggregates areemployed. Thls process would not serve in utilities to which the hereinimprovement a sufiicient increased hardness and toughness can besecured, to serve in making concretes for the entire territory of thecountry.'

In building highways, especially, light,

portable crushers would follow, from ledge to ledge, of the lighter rockand provide broken aggregates, along the way, as the building of thehighway would proceed, thus saving large costs in the constructionthereof. The lighter stones, referred to, are very discursive and mightbe found to serve, conveniently, the entire demand of the United States.These consummations are very much to be desired, and will be of greatservice in many utilities, especially in highways and streetconstructions.

Having described my method what I claim 1s The process of toughening andhardening lighter mineral aggregates to increase their coefiicienc-ywhich comprises treati-n said aggregates in a clean condition witcalcium oxide whilst in the aet of-slaking, in the approximatevproportion of ten pounds of calcium oxide to five hundred pounds'of'ag'gregates.

In testimony whereof, I have hereunto signed my name. i

JOSEPH HAY AMIES.

